1. Field of the Invention
The present invention relates to a large current fuse which is employed in a vehicle such as an automobile.
2. Description of the Related Art
A large current fuse as disclosed in Japanese Patent Publication No. 2637846 has been widely known as a conventional large current fuse of this type.
A structure of the large current fuse disclosed in the Japanese Patent Publication will be briefly described hereunder referring to FIGS. 10 and 11.
In FIG. 10, the large current fuse 1 comprises a metallic fusing member 2 and a pair of resin covers 3, 3. The metallic fusing member 2 is integrally formed of a metal plate having electric conductivity, and electrically connected and fixed to a connecting part of a mating component (not shown) by means of stud bolts 4 and nuts 5. The resin covers 3, 3 are overlapped on the metallic fusing member 2 from a front and a back sides of the metallic fusing member 2, and bonded by ultrasonic welding.
In FIG. 11, the metallic fusing member 2 includes a first conductive plate 6, a second conductive plate 7, and a fusing part 8. The first conductive plate 6 and the second conductive plate 7 are respectively provided with mounting holes 9 having a large diameter and welding pin holes 10, 10 having a small diameter.
The fusing part 8 is formed in an S-shape between the first conductive plate 6 and the second conductive plate 7 with its opposite ends connected to the first conductive plate 6 and the second conductive plate 7. A fusible member 11 is disposed in the middle of the fusing part 8.
The resin cover 3 is so designed as to extend over the first conductive plate 6 and the second conductive plate 7 and to be higher at its central part in a side elevational view. The resin cover 3 includes fixing parts 12, 12 to be fixed to the first conductive plate 6 and the second conductive plate 7, a part 13 forming a space for containing the fusing part 8, a longitudinally extending rib 14, and a guide 15 corresponding to the rib 14.
The fixing parts 12, 12 are respectively provided with welding pins 16 and holes 17 for receiving the pins 16.
The part 13 is formed between the fixing parts 12, 12 continuing therefrom and defines the space for containing the fusing part 8. A recess 18 is formed in the space defining the part 13 on a side facing with the fusing part 8.
It is to be noted that the resin covers 3, 3 can be commonly used even in case where the fusing part 8 is modified to any shape having electric resistance value corresponding to the rated current.
In the prior art as described hereinabove, a welding assembling machine has been additionally required for assembling the resin covers 3, 3, and a cost for installing the welding assembling machine has been a factor of high cost.
Moreover, since the metallic fusing member:2 and the resin covers 3, 3 are not integrally formed in a strict sense, sufficient rigidity cannot be obtained. When a torsion force is applied to the large current fuse 1, the metallic fusing member 2 is likely to be deformed in a torsion direction. The large current fuse 1 has been of such a structure as being easily influenced by environments.
As a countermeasure, it has been considered that the resin covers 3, 3 of synthetic resin are integrally formed with the metallic fusing member 2, in view of assembling steps of the resin covers 3, 3 to the metallic fusing member 2 and number of steps for molding the resin covers 3, 3.
However, because a width D of the fusing part 8 at areas continuing to the first conductive plate 6 and the second conductive plate 7 is variable according to the rated currents, a molding die exclusive for each of the rated currents has been necessary in order to secure the space for containing the fusing part 8. Therefore, this has not been a perfect countermeasure.
Meanwhile, as apparent from the described. structure, the resin covers 3, 3 are not so constructed that a state of the fusing part 8 can be visually observed, and heat generating in the metallic fusing member 2 cannot be completely radiated.
The present invention has been made to overcome the above described problems, and it is an object of the invention to provide a large current fuse which does not require exclusive molding dies for molding respective resin housings according to the rated currents. A large current fuse in which a state of a fusing part can be visually observed and having high radiation efficiency is provided at the same time.
According to the invention, there is provided a large current fuse which comprises a metallic fusing member integrally formed of a metal plate having electric conductivity, a resin housing formed of synthetic resin and integrally molded with the metallic fusing member, the metallic fusing member including a first conductive plate formed in such a shape as corresponding to an electrically connecting part of a mating component, a second conductive plate formed in such a shape as corresponding to another electrically connecting part and spaced from the first conductive plate, and a fusing part positioned between the first conductive plate and the second conductive plate, formed in such a shape as having electric resistance value according to a rated current, and adapted to be fused by an over current thereby to open a circuit, the resin housing being formed extending from a front face to a back face of the first conductive plate, from a front face to a back face of the second conductive plate, and between the first and second conductive plates, and having an open space through which the fusing part is exposed, a first projecting piece continuing to the fusing part being formed on a side face which is a thickness of the first conductive plate facing with the second conductive plate, the first projecting piece projecting toward the second conductive plate by way of an edge defining the open space, a second projecting piece continuing to the fusing part being formed on a side face which is a thickness of the second conductive plate facing with the first conductive plate, the second projecting piece projecting toward the first conductive plate by way of the edge, a width of the first projecting piece in a direction perpendicular to its projecting direction and a width of the second projecting piece in a direction perpendicular to its projecting direction being of a fixed size, irrespective of the rated current.
According to a second aspect of the invention, at least one of the first projecting piece and the second projecting piece is provided with an opening passing from a front face to a back face thereof.
According to a third aspect of the invention, the width of the first projecting piece and the width of the second projecting piece are broader than portions of the fusing part continuing from the first projecting piece and the second projecting piece.
According to a fourth aspect of the invention, at least one small hole passing from the front face to the back face is respectively provided at areas of the first conductive plate and the second conductive plate on which the resin housing is molded.
According to a fifth aspect of the invention, a plurality of fins are formed on the resin housing at least at areas on which the resin housing is molded on the first conductive plate and the second conductive plate.
According to the invention, there is provided the large current fuse consisting of the metallic fusing member and the resin housing integrally formed therewith.
Because the resin housing is formed extending from the front face to the back face of the first conductive plate, from the front face to the back face of the second conductive plate, and between the first and second conductive plates, the resin housing will not be deformed by an outer force or environmental condition.
Further, because the resin housing has the open space through which the fusing part is exposed, the fusing part can be visually observed.
The first conductive plate is provided with the first projecting piece having a fixed width and the second conductive plate is provided with the second projecting piece having a fixed width. Accordingly, the molding die of the resin housing will not be influenced by the shape of the fusing part, and there is no need of providing the molding dies exclusively for respective rated currents.
According to the second aspect, the structure is useful in setting the electric resistance value of the fusing part according to the rated current. Moreover, a difference in expansion and contraction by heat between the resin and the metal can be absorbed by the opening.
According to the third aspect, the first and the second conductive plate can be utilized as heat radiation plates.
According to the fourth aspect, the synthetic resin flows into the small holes passing from the front face to the back face, and the resin housing will be strengthened.
According to the fifth aspect, by providing a plurality of the fins, the radiation efficiency will be improved as compared with the conventional large current fuse.